Micromachined pressure sensor and method of making the same

A micromachined TFPS comprised of

• a. A silicon substrate (100) with silicon nitride as the membrane structural materials (210) for the said diaphragm structure to achieve the thermal sensing mechanical configurations;
• b. An integrated micro-heater (300) and pairs of temperature sensors or thermistors (310/315 and 320/325) deposited on the membrane of silicon nitride, comprising of platinum or poly-silicon materials with interconnection (410/420) made of gold or aluminum materials;
• c. A passivation layer (500) of silicon nitride on top of the micro-heater and the temperature sensors or thermistors;
• d. A thermal insolation layer made of zirconia oxide (600) on top of the passivation layer to provide insulation for the reduction of media interference;
• e. An additional surface passivation layer (650) made of silicon nitride to protect the device from attacking by corrosive agent;
• f. An access or opening (700/710) for connecting the TPFS to control electronics;
• g. A cavity 800 beneath the membrane of the diaphragm structure provides the sensing reference as well as thermal isolation for boost of device response time;
• h. When integrating the TFPS with a thermal flow sensor additional mask and etch step is applied to remove thermal isolation layer and the additional passivation over the flow sensing area with openings as pressure balance.